1. Field of Invention
The present invention relates to a simple, efficient and reliable method of obtaining novel poly(vinyl halide) resins having reduced molecular weight, low polydispersity, and good thermal stability by mimicking a "living" radical polymerization mechanism.
2. Description of the Art
The addition of hydrogen iodide to vinyl chloride was first described by Kharasch and Hannum in an article in 1934. The article, entitled "The Peroxide Effect in the Addition of Reagents to Unsaturated Compounds IV. The Addition of Halogen Acids to Vinyl Chloride", J. American Chem. Soc., 56, (1934) p. 712 described the addition of various halogen acids such as hydrogen iodide to vinyl chloride. In particular, Kharasch et. al. discuss the addition of 0.12 moles of hydrogen iodide to 0.1 mole of vinyl chloride in a reactor. Kharasch et. al. were studying the effects of peroxides on reactions which occur via a carbonation process in contrast to the present invention for free radical processes.
An attempt was made to reproduce the work of Kharasch and Hannum using pure reagents. Using the Kharasch procedure, there was no 1-chloro-1-iodoethane synthesized. However, applicants have discovered a novel process for synthesizing 1-chloro-1-iodoethane. The 1-chloro-1-iodoethane is useful as an iodine containing chain transfer agent in the polymerization of vinyl chloride, resulting in a vinyl chloride polymer having good thermal stability along with low molecular weight and low polydispersity.
Logothetis, in an article in Progressive Polymer Science Vol. 14, 1989, pp 251-296 Pergammon Press p/c describes the use of iodofluorohydrocarbons in radical polymerizations of fluorine containing monomers. Lower polydispersity elastomer fluoropolymers were reported using perfluoroalkyl iodide transfer agents.
Similarly, Tatemoto et. al. in U.S. Pat. No. 4,158,678 have disclosed segmented polymers and their formation using at least one fluorine containing segment. The segmented polymers comprise an iodine atom liberated from an iodinated compound.
German Patent No. 2,045,491 to Klinkenberg and Schrage describes the polymerization of vinyl chloride in the presence of exclusively secondary alkyl iodides at temperatures below zero degrees Celsius in order to reduce the molecular weight of the polyvinyl chloride conventionally formed at that temperature range. According to Klinkenberg et. al., vinyl chloride is polymerized at low temperature in bulk using a boron oxidizing agent as the initiator. The reaction is effected in the presence of acyclic and cyclic secondary alkyl iodides of the formula R'--CHI--R", where R' and R" are alkyl, aryl or arylalkyl or where R'+R"=--(CR.sub.2).sub.x -- X.gtoreq.3, R=H, aryl, or arylalkyl and the total number of carbon atoms is approximately 3 to 15, preferably 3 to 6.
U.S. Pat. No. 3,983,187 to Moczygemba et. al. discloses the use of iodine or organic iodines for use as molecular weight regulators in copolymerization systems. Moczygemba et. al. use the iodine weight regulators in the suspension co-polymerization of styrene-containing monomers. This patent however is silent regarding forming poly (vinyl halide) using iodine containing chain transfer agents.
British Patent No 674,060 published in 1952 discloses polymerization of vinyl chloride in the presence of iodoform (CHI.sub.3).
After many repeated trials using Iodoform it was found that widely varying results were obtained. In unexplained fashion, several trials failed to achieve any conversion of monomer or any reduction in molecular weight and no methods were obtainable to gain control over the process.